Downspout for bubble trays



p 1 c. G. GERHOLD 2,385,3

DOWNSPOUT FOR BUBBLE TRAYS Filed Nov. 15, 1945 Patented gent 2%, i5

rcs ssss DOWNSPOUT FOR BUBBLE TRAYS Clarence G. Gcrhold, Chicago, 111., asslgnor to Universal Oil Products Company, Chicago, lit, a corporation oi. Delaware Application November 15, 1943, Serial No. 510,284

6 Claims. (Cl. 261-110) This invention relates to an improvement in fractionating columns. and more particularly to an improved form of downspout for bubble trays employed in fractionating columns, absorption columns, and the like.

The present invention provides for an improved type of downspout which makes possible a more eflicient utilization of the bubble tray area.

The present invention also eliminates any possibility of accumulations of sediment on the individual bubble trays. Any sediment which may be present in the feed to the column is drained oil from each tray and removed from the bottom of the column.

The present invention provides a novel downspout in which a portion thereof is utilized as cilective head to induce the flow of liquid from the bubble tray into the downspout whenever the height of the liquid level upon the tray rises above a certain predetermined point. When the liquid on the tray is below this predetermined 'point, only the height of liquid above the tray is effective as head for inducing flow into the downspout. The increased head 'eflected by the novel arrangement of the downspout which is herein presented makes possible the use of smaller downspouts, thereby releasing more tray area for bubble caps. Also, by withdrawing fluid from the bottom of the liquid on the tray, less entrained vapors and foam must be carried by the downspout. In conventional downspouts this entrained foam and vapor presents a dimcult problem and makes necessary the use of design factors which take into account the transportation of this foam from one tray to the next through the down-- spouts and results in relatively large size downspouts.- A

In order to make the features and advantages of the invention more apparent and clearly understood, reference is made to the accompanying diagrammatic drawing in which Figures 1 and 2 illustrate fragmentary sectional views of free-- tionating columns showing two different forms of downspouts which come within the scope of the invention.

Referring to Figure 1, the main shell of the iractionating column is indicated by i and dis posed therein are bubble trays 2 and t. The bubble trays are securely attached to the fractionating column shell by welding or other suitable means. Conventional vapor risers and hubhle caps i and 5 respectively are provided in the bubble trays, the bubble cap being secured by means of hold-down bar ii which is attached to the wall of the fractionating column or to the 0 line l2.

bubble tray by bolts or other suitable means not shown.

Passing through tray 2 is an elongated conduit 1 which terminates a short distance above tray 3 to allow passing of fluid on to the latter. The upper end of conduit 1 is closed by means of cap I which is provided with a plurality of ports 9, the purpose of which will be later explained.

Around the periphery of conduit 1 immediately above tray 2 are a series of ports l0 through which liquid may flow from above tray 2 into the conduit and thence down to tray 3. Concentrically disposed within conduit 1' is another conduit II which is open at both ends. The lower end of conduit Ii terminates a substantial distance .below tray 2 but above the normal liquid level within conduit 1 which is indicated by broken The upper end of conduit ll extends to a suitable distance above the normal liquid Kid level on tray 2. The total area of ports 9 and ill should preferably be at least as large as the cross-sectional area of the annular space between conduits i and H where they intersect the plane of tray 2.

In operation, the downspout will function as follows: The flow of liquid down the column is normally at such a rate that ports I!) are insufficient to carry it all away from the tray when the liquid level is at a height indicated by broken line It. In this case the effective head which governs the flow through ports in is indicated at hi. Because the flow through ports ill is less than the normal flow down the column,the liquid level on the tray will tend to build up until it reaches a height indicated by broken line it. When this occurs, ports 9 are closed, thus preventing the entry of vapors into the annular shaped portion of the downspout and the entire upper annular shaped portion of the downspout between conduits I and II from closure member ii to the lower end of conduit it will fill with liquid. This will in turn change the effective head on ports it from hi to ha and will result in a considerable increase in flow from tray 2 into and down the downspout. By selecting suitable sized ports 9 and it, this increased rate can be made considerably in excess of the normal flow of liquid down the column and will, therefore, cause the liquid level on tray 2 to return tothe height indicated by broken line it. When the liquid level again reaches the height indicated by broken line 63, ports 9 are uncovered, thus releasing the liquid in the upper portion of the downspout and changing the effective head on ports it to in. This cycle of events will conprises an elongated conduit member 2% which is secured to tray 2 and extends downward to a short distance of tray s. Within conduit member 2% is a second conduit 2! which extends from above the normal liquid level on tray 2 downwardly to within a short distance of the lower end of conduit member 28. Conduit 2! is supported from conduit member 26 by a plurality of webs 22 which are attached thereto by welding or other suitable means. Conduit meme .ber .20 terminates at tray! and a second conduit member of decreased size 23, extending from a point above tray 2 up to approximately the lower liquid level indicated by broken line 24, completes the outer conduit corresponding to con duit 1 in- Figure 1. Approximately at the upper liquid level indicated by broken line 25 is a closure plate 26 which is secured by welding or other suitable means to conduit 2|. Between conduit member 23 and member 28 is provided a continuous port 21 for the flow of fluid into the downspout and between the upper end of conduit member 20 and the lower end of conduit member- 23 ls'provided a series of ports.

In this particular form oi the invention, the cross-sectional area of the annular space between conduit 2| and conduit member 23 is approximately the same or less than the cross-sectional area of port 21 and the cross-sectional area of the annular space between conduit 2! and conduit member 26 is approximately equal to or less than the total combined area of port 21 and ports 28. By thus limiting the cross-sectional area of the downspout at the tray level, filling of the annular space between conduit 2| and member 20 is assumed and the increased effective head In obtained.

The inner conduit in the downspout allows the return of vapors separated in the lower portion thereof back to the vapor space If claim as my invention:

1. In a fractionatlng column provided with a plurality of vertically spaced bubble trays, downspouts for said trays each of which comprises in combination a vertically disposed conduit extending through one of said trays provided with a closure member at its upper end and open at its lower end, the Tlowerend of said conduit terminating at a point substantially below said tray but above the next lower tray in said fractionating column, said conduit being provided with at least one port therethroush at a point immediately above said tray but below the normal liquid level to be maintained thereon, said conduit being provided with at least one port positioned approximately at said liquid level and a second conduit extending vertically downward from a point substantially above said normal liquid level through said closure means to a point a subabove the tray.

aseasss stantial distance'below said first mentioned tray but terminating short of the lower end of said first mentioned conduit.

2. In a fractionating column provided with a plurality of vertically spaced bubble trays, downspouts for said trays each of which comprises in combination a vertically disposed conduit extending through one of aid trays provided with a closure member at its upper end and open at its lower end, the lower end of said conduit termihating at a point substantially below said tray but above the next lower tray in said fractionating column, said conduit being provided with a plurality of ports therethrough at a point immediately above said tray but below the normal liquid level to be maintained thereon, said conduit being provided with a plurality of ports positioned approximately at said liquid level and a second conduit extending vertically downward from a point substantially above said" normal liquid level through said closure means to a point a substantial distance below said first mentioned tray but terminating short of the lower end of said firstmentloned conduit.

3. In a fractionating column provided with a plurality of vertically spaced bubble trays, downspouts ior said trays each of which comprises in combination a vertically disposed conduit extend ingthrough one of said trays provided with a closure'member at its upper end and open at its lower end, the lower end of said conduit terminating at a point substantially below said tray but above the next lower tray in said fractionating column, said conduit being provided with a a plurality of ports therethrough at a point immedlately above said tray but below the normal liquid level to be maintained thereon, said conduit being provided with a plurality of ports posltio'ned approximately at said liquidlevel and a second conduit extending vertically downward from a point substantially above said normal liquid level through said closure means to a point a substantial distance below said first mentioned tray but terminating short of the lower end or said first mentioned conduit, said second mentioned conduit being concentric with the first mentioned conduit.

.4. The device defined in claim 3 further characterized in that thetotal cross-sectional area or said ports is at least equal to the cross-sectional area of that portion of the downspout confined between the first and second mentioned conduit at the point of their' intersection with the plane of said tray.

5. The device defined inclaim 3 further charracteriz'ed in that the annular space between the first and second mentioned conduits is of reduced cross=sectlonal area in that portion thereof which is above the first mentioned ports.

-6. The device defined in claim 3 further characterized in that the cross-sectional area of the second mentioned ports is at least as great as the cross-sectional area of the annular space between the first and second mentioned conduits in that portion which is above the first, mentioned p rts.

CLARENCE G. GERHOLD. 

